Is this normal for lactating mom?

hi again, okay, now i have another problem with my momma cat. kittens are almost six weeks old, still suckling but also eating science diet natures recipie for kittens. I have also been feeding mom the same diet. today I have noticed a very large lump on her tummy, surronding one nipple and going for about three or four inches across, under her skin. feels hard, and just about a week or two ago it was not there. I am sorry to say, since one of her kittens was very sick, I did not pay attention to mom as much as i should. kitten kept me very very busy. when i picked Mystique the momma up today, i felt the large lump, feels kinda hard. vets are closed until tuesday, she is not in pain, still eating, and otherwise seems healthy. i didn't even know something was wrong until i picked mom up. besides the fact she always seems hungry. I know their are alot of breeders out there and was wondering if any have experienced any of this. I am worried this may be a tumor, but I have rats which get tumors quite often, and it usually takes a long time to be big. (i do put them to sleep when the tumor gets in the way of their life.) But I am still worried, and don't want to be worried sick over the weekend. I looked in the cat owners vet. handbook, which my neighbor loaned me, and can't find too much on lactating problems. I hope someone can feed me some ideas, but i do know no one but a vet can tell me for sure. I am still worried sick, and already spent about 300 dollars on vet care for the kitten, and paying on payments for that. (which sorry to say, my little angel did not make it.) I will be watching her very closely, thanks to anyone that may be able to help.

i honestly have clue.... maybe its a gland thing???? experts should be around to help though

is it hot to the touch? Swollen and looking painful? Are there purple discoloration marks around it? If yes to any of these question please find a vet quickly as it could be mastitis

None of those symptoms, thank god, or she would have already been to the vet. doesn't appear painful to the touch either.

My cat has this as well. Her kittens left last week and the nipple they fed from has become swollen and hard. She seems otherwise fine. No pain when I touch the area, no purple colour, no discharge, eating well, no temperature and active. Will the swelling go down by itself or do I need to take her to the vet?

Could it be an abcess from a kitten bite? I'm not too sure if it's possible, but that's what it sounds like to me... an abcess.